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x86/stacktrace: Fix reliable check for empty user task stacks
[ Upstream commit039a7a30ec
] If a user task's stack is empty, or if it only has user regs, ORC reports it as a reliable empty stack. But arch_stack_walk_reliable() incorrectly treats it as unreliable. That happens because the only success path for user tasks is inside the loop, which only iterates on non-empty stacks. Generally, a user task must end in a user regs frame, but an empty stack is an exception to that rule. Thanks to commit71c9582528
("x86/unwind/orc: Fix error handling in __unwind_start()"), unwind_start() now sets state->error appropriately. So now for both ORC and FP unwinders, unwind_done() and !unwind_error() always means the end of the stack was successfully reached. So the success path for kthreads is no longer needed -- it can also be used for empty user tasks. Reported-by: Wang ShaoBo <bobo.shaobowang@huawei.com> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Wang ShaoBo <bobo.shaobowang@huawei.com> Link: https://lkml.kernel.org/r/f136a4e5f019219cbc4f4da33b30c2f44fa65b84.1594994374.git.jpoimboe@redhat.com Signed-off-by: Sasha Levin <sashal@kernel.org>
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1 changed files with 0 additions and 5 deletions
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@ -58,7 +58,6 @@ int arch_stack_walk_reliable(stack_trace_consume_fn consume_entry,
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* or a page fault), which can make frame pointers
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* unreliable.
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*/
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if (IS_ENABLED(CONFIG_FRAME_POINTER))
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return -EINVAL;
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}
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@ -81,10 +80,6 @@ int arch_stack_walk_reliable(stack_trace_consume_fn consume_entry,
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if (unwind_error(&state))
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return -EINVAL;
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/* Success path for non-user tasks, i.e. kthreads and idle tasks */
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if (!(task->flags & (PF_KTHREAD | PF_IDLE)))
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return -EINVAL;
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return 0;
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}
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